Manufacture of microporous articles



Feb. 18, 1941. w. A. GIBBONS 2,232,109

MANUFACTURE OF MICROPOROUS ARTICLES Filed May 12, 1938 INVENTOR. W/ZZ/J 4. 6755014! ATTORNEYS Patented Feb. 18, 1941 I UNITED STATES PATENT OFFICE MANUFACTURE OF MICROPOROUS ARTICLES Willis A. Gibbons, Montclair, N. 3., assignor, by mesne assignments, to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application May 12, 1938, Serial No. 207,483

4 Claims. (Cl. 18-53) This invention relates to the manufacture of Sheet. A liner, usually fabric, is then unrolled microporous articles, more particularly battery from a drum E and applied to the composite plasplate separators, from heat-hardenable plastics tic sheet and powder, and afterwards the entire patterned with designed areas, prior to curing or assembly is rolled up on a drum F. The drum F 5 setting. carrying the rolled-up assembly (including the 5 More particularly the invention relates to a temporary talc filling for the depressed areas in method of retaining the shape or contour of said the sheet) is afterwards immersed in water or designed areas of said plastics during the heating steam heated to a vulcanizing temperature to or curing thereof. For example, in the manufaccure the rubber and develop microporosity in the ture of battery plate separators which have a rubber. l0 predetermined contour impressed or engraved or If desired, water may be applied to the tale otherwise created thereon, for example in the coating after it has filled the valleys, as by sprayform of ridges or corrugations, an object of the ing water thereon, either before, during or after invention is to hold the impressed or engraved dethe application of the fabric liner from drum E.

sign in place and maintain its sharp definition Another variation is to immerse the drum con- 15 while heat-hardening the plastic. This object taining the wrapped composite assembly of plasis attained herein by spreading on the profiled tic sheet and powder in water prior to or during base of the sheet a layer or coating of substanthe vulcanization stage. After vulcanization, tially dry finely divided or powdered water-inthe material used to maintain the profile, for exsoluble solid material so as to fill the depressed ample talc, is washed off or otherwise removed 20 areas and form at least a thin layer over the from the surface of the vulcanized sheet, and raised areas. the sheet is cut into finished separators of the Thereafter the composite plastic sheet,in the dimensions desired. case of rubber, containing sulphur suflicient to Rubber products fashioned, treated and cured form hard rubber,-is vulcanized under condiaccording to the present invention have even, 25 tions which confine the mass under positive reundisturbed surfaces, with the sharpness of the straining forces until a hard rubber vulcanizate profile design faithfully preserved. has been obtained. Such a procedure may con- .Examples of other fillings than talc, which act sist of rolling the'composite sheet up on a drum as a temporary matrix and which are usable in with or without a cloth liner to separate the laythe process, are whiting or other forms of cal- 30 0 p y Stacking the composites 0n trays 0r cium carbonate; finely divided silica, such as inin a number of layers, one upon another. For fusorial earth; natural silicates, such as talc or the production of microporous articles, cures are clays. Inv general, one may use any finely dica ed 0111? u er non-evaporative ns; vided substantially dry solid which is substaneith r open steam or submarine e m y be use tially inert chemically toward rubber or other in- 35 as set forth in U. S. P. N0. 2,112,529, wherein hygredients ccmpounded therein, drophilic colloids such as bentonite are used for The advantages of using from the beginning developing microporosity; The introduction and substantially dry temporary filling such as talc disseminat n of W e throughout e s ay instead of wet pastes are several. The wet paste also be obtained by the addition of colloids havincludes higher costs of preparation, requires 40 ing associated water, for example hydrous silicic more lab t o t of th physical properacid gels, prior to Shaping and curing ties of the wet paste, and in general is more com The plastic zed rubber compounded with V plicated in application than the original use of canizing ingredients such as bentonite or the substantially d d 4s drous si i ic cid as shown in the Having thus described my invention, what I aw 15 given the desired P by Passage claim and desire to protect by Letters Patent is: through a suitably engraved calendered roll or 1. A method of manufacturing from trolls A. The ribbed or corrugated sheet is then hardenable m t stock, articles having predeconvey d al a t B under a mechanism 0 termined relief designs in the surface thereof,

consisting of a container from which powder, for which comprises forming h design areas d 50 example tale, is flowed onto the sheet either by applying a temporary filling of substantially dry ravi y o by mechanical feed, and a scraper D finely divided water-insoluble material to such levels fi the Powder in the desired manner- If areas to fill and cover over at least the valleys des re a known vibrator knife attachment may of the surface design, curing or setting the plasbe used for applyi g e powder to the calendered tic while said filling is confined in association 55 with the surface of the plastic under positive restraining pressure, said filling acting as a temporary matrix to maintain the definition of the design, and thereafter removing the temporary filling.

2. A method of manufacturing from heathardenable plastic stock, articles having predetermined relief designs in the surface thereof, which comprises forming such design areas and applying a temporary filling of substantially dry finely divided water-insoluble material to such areas to fill and cover over at least the valleys of the surface design, then wetting the filling, our

ing or setting the plastic while said filling is confined in association with the surface of the plastic under positive restraining pressure, said filling acting as a temporary matrix to maintain the definition of the design, and thereafter removing the temporary filling.

3. A method of manufacturing a rubber article bearing relatively sharply depressed surface areas which comprises forming such areas and composition into sheet form having such reenfor'cer'nents, applying a coating of a substantially dry finely divided water-insoluble material to the ribbed or corrugated surfaces so as to fill the valleys and form an even surface over the sheet, and confining the coated sheet so as to keep the coating intact during subsequent operations including curing the rubber under non-evaporative conditions.

WILLIS A. GIBBONS. 

